The invention concerns circuitry for electronically commutating a multiphase direct-current motor, whereby markers are distributed around the circumference of a rotor, the markers provide, in conjunction with a sensor, the commutating pulses that activate the motor's phase conductors, the pulses supplied by the sensor advance a counter that has output terminals, the output terminals control switches that switch the phase conductors alternately to operating and to reference voltage, and the counter re-zeroes itself after a certain number of pulses. Circuitry of this type is known. It is described for example in German OS No. 3 435 270. Its purpose is to activate the motor's various phase conductors at appropriate instants. The markers on the circumference of the rotor can be light-permeable or reflecting points that operate in conjunction with light-sensitive sensors or they can be permanent magnets that act on a sensor in the form of a Hall generator. The markers generate a periodic sequence of pulses that activate the phase conductors, which a counter cyclically connects by way of bipolar switches to either operating voltage or reference voltage. The sequence is constructed when the counter re-zeroes itself subsequent to a certain number of pulses that is a whole-number divisor of the number of markers.
Sometimes, however, the counter will re-zero itself a pulse too early or too late, preventing optimum activation of the phase conductors. It is then no longer possible to attain optimum torque, and the efficiency of the motor is detrimentally affected.